GM Service Manual Online
For 1990-2009 cars only

Step

Action

Yes

No

Schematic Reference: Headlights/Daytime Running Lights (DRL) Schematics

1

Did you perform the Lighting System Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - Lighting Systems

2

  1. Turn OFF the ignition.
  2. Place the headlamp switch in the OFF position.

Are the low beam headlamps or high beam headlamps illuminated?

Go to Step 3

Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

3

  1. Place the headlamp dimmer switch in the low beam position.
  2. Observe the headlamps.
  3. Place the headlamp dimmer switch in the high beam position.
  4. Observe the headlamps.

Do the low beam headlamps and the high beam headlamps illuminate when they are selected?

Go to Step 5

Go to Step 4

4

Are only the low beam headlamps illuminated?

Go to Step 9

Go to Step 10

5

Remove the automatic lamp control (ALC) headlamp relay.

Are the headlamps illuminated?

Go to Step 6

Go to Step 7

6

Test the automatic headlamp low control circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 13

Go to Step 8

7

Inspect for poor connections at the ALC headlamp relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 13

Go to Step 11

8

Inspect for poor connections at the harness connector of the turn/headlamp switch. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 13

Go to Step 12

9

Repair a short to ground in the headlamp low beam signal circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 13

--

10

Repair a short to ground in the headlamp high beam signal circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 13

--

11

Replace the ALC headlamp relay. Refer to Relay Replacement in Wiring Systems.

Did you complete the replacement?

Go to Step 13

--

12

Replace the turn/headlamp switch. Refer to Multifunction Turn Signal Lever Replacement - On Vehicle in Steering Wheel and Column.

Did you complete the replacement?

Go to Step 13

--

13

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 2